1. The problem statement, all variables and given/known data Determine the speed of an electron in a hydrogen atom (radius .5 * 10^-10 m) and state if it is relativistic. (Treat the electron as through it were in a circular orbit around the proton.) (Given that .1c and greater is relativistic) 2. Relevant equations not sure... L=L0 (1-v^2/c^2)^1/2 a=v^2/r ? 3. The attempt at a solution I don't really know where to start. I assume the fact that the electron has a centripetal acceleration and velocity comes into play somehow.